This application is an application under 35 U.S.C. Section 371 of International Application Number PCT/FR97/01979, filed on Nov. 5, 1997.
The subject-matter of the present invention is novel crosslinkable compositions for forming novel polyurethane films comprising functionalized silicone oils and the use of the novel polyurethane films as protective coating, in particular for car bodies, boat hulls, the bodies of household goods and appliances, or any other surface.
Protective coatings have to possess numerous qualities combining both aesthetic and visual appearances and properties of resistance to external influences. A first fundamental criterion of effectiveness for protective coatings is the ability to withstand acids, in particular in the case of car paints or varnishes; the latter have to withstand the action of acid rain. A second fundamental criterion of effectiveness relates to the hydrophobic qualities, which, of course, must be high. A third fundamental criterion is the resistance to mechanical stresses, such as the resistance to scratching.
Numerous coating or paint compositions comprising silicone oils have been provided. The compositions of U.S. Pat. No. 5,268,215 or those of Patent EP 531,463 should in particular be noted; however, these do not exhibit all the qualities required which make it possible to obtain stable protection which is lasting over time. In addition, these compositions sometimes have to be used in a rigorous and complex way for an application which does not guarantee minimum effectiveness.
The object of the present invention is to provide novel crosslinkable compositions in order to form polyurethane films. These novel crosslinkable compositions, which comprise functionalized silicone oils, have qualities, evaluated according to the criteria above, which are improved with respect to the known compositions of the prior art. In addition, the novel crosslinkable compositions are relatively quick to prepare and are easy to use.
A marked improvement in quality and stability of the properties of resistance to acids, of the properties of resistance to mechanical stresses, such as the resistance to cracking, and of the hydrophobic properties is observed for the novel polyurethane films resulting from the crosslinkable compositions of the invention.
The novel crosslinkable compositions according to the invention comprise:
(a) 20 to 50 weight % of polyisocyanate,
(b) 50 to 80 weight % of acrylic oligomer comprising hydroxyl groups, the content by weight of which with respect to the acrylic oligomer is between 2.5 and 4.5%,
(c) 1 to 10 weight % of a silicone oil of formula (I): 
xe2x80x83in which:
(1) o and p are identical or different integers of between 1 and 100 and preferably from 1 to 50,
(2) 1 represents an integer such that 1=2+q,
(3) q represents an integer of between 0 and 10,
(4) m represents an integer of between 1 and 60, preferably between 1 and 30, particularly preferably from 1 to 10,
(5) n is an integer such that 20 less than (100xc3x97m)/(m+n) less than 60, preferably 25 less than (100xc3x97m)/(m+n) less than 55,
(6) the symbols R1 and R2 are identical and/or different and represent a hydrocarbon-comprising radical chosen from linear or branched alkyl radicals having from 1 to 4 carbon atoms, linear or branched alkoxy radicals having from 1 to 4 carbon atoms, aryl radicals or alkylaryl radicals and preferably a methyl radical, a phenyl radical, a methoxy radical or an ethoxy radical,
(7) the symbols R3 and R4 are identical and/or different and are chosen from:
monovalent xe2x80x94(CH2)hxe2x80x94Sixe2x80x94(R1)3 radicals where h is between 1 and 10, preferably from 1 to 3,
monovalent aromatic alkylaryl radicals, the linear or branched alkyl part comprising 1 to 4 carbon atoms, the symbol R3 preferably representing the monovalent xe2x80x94CH(CH3)C6H5 radical and the symbol R4 preferably representing the monovalent xe2x80x94CH2CH2C6H5 radical,
(8) the symbols R5 and R6 are identical and/or different and represent a monovalent functional group chosen from:
a monovalent primary amine of xe2x80x94R7xe2x80x94NH2 type where R7 is a linear, branched or cyclic alkyl radical having from 1 to 6 carbon atoms,
a monovalent secondary amine of xe2x80x94R8xe2x80x94NHxe2x80x94R9 type where R8 and R9, which are identical and/or different, are linear, branched or cyclic alkyl chains having from 1 to 6 carbon atoms,
a monovalent xe2x80x94(CH2)a(NHCH2CH2)bNH2 radical where a and b are independent integers:
a is between 1 and 10, preferably 1 to 3,
b is between 0 and 10, preferably 0 or 1,
a monovalent xe2x80x94(CH2)c(OCH2CH2)d(OCH2CHCH3)eOH radical where c, d and e are independent integers:
c is between 1 and 20, preferably 1 to 10,
d is between 0 and 70, preferably 0 to 12,
e is between 0 and 70, preferably 0 to 15,
a monovalent xe2x80x94(CH2)fSH radical where f is an integer which can range from 1 to 10, preferably from 1 to 3,
a monovalent xe2x80x94(CH2)gxe2x80x94C(R)2xe2x80x94OH radical where g is an integer which can range from 1 to and preferably from 1 to 3, and Rxe2x80x2 represents a hydrocarbon-comprising radical chosen from a linear or branched alkyl radical having from 1 to 4 carbon atoms, aryl radicals and alkylaryl radicals.
The values of percentages by weight relating to the compounds (a), (b) and (c) refer to the content of total solid matter in the crosslinkable composition, i.e. the solid matter of the three compounds (a), (b) and (c).
According to an advantageous form in accordance with the invention, the properties of resistance to scratching are optimized with a crosslinkable composition comprising (a) 20 to 40 weight % of polyisocyanate, preferably 30%, (b) 60 to 80 weight % of hydroxylated acrylic oligomer, preferably 70%, and (c) 1 to 4 weight % of a silicone oil of formula (I), preferably 2 to 3%, such that the NCO/XH molar ratio in the polyurethane films is between 0.5 and 2 and preferably between 0.80 and 1.1. NCO is the isocyanate functional group of the polyisocyanate and XH represents OH, NH and SH, which are the reactive functional groups of the acrylic polymer and those of the functionalized silicone oil.
The acrylic oligomer generally comprises between 0.1 and 10 weight % of hydroxyl groups. This percentage of hydroxyl groups is advantageously between 1 and 6% and more particularly between 2.5 and 4.5%.
The crosslinkable composition generally comprises a solvent such that the percentage by weight of the compounds (a), (b) and (c) with respect to the crosslinkable composition comprising a solvent is between 40 and 80% and preferably of the order of 50 to 60%. Various types of solvent can be used, for example methyl amyl ketone, butyl acetate and the product Solvesso 100 (resulting from a petroleum fraction).
The structure of the silicone oil present in the composition according to the invention is chosen such that the said oil is weakly miscible in the system composed mainly of the mixture of acrylic oligomer and of polyisocyanate. On this subject, the presence of the 2-phenylethyl and 1-phenylethyl groups within the structure of the silicone oil controls the degree of miscibility of the chain of the silicone oil in the acrylic oligomer and polyisocyanate system. The level of Si units of the silicone oil modified by these groups varies from 20 to 40%.
In addition, according to another advantageous form of the invention, the crosslinkable composition comprises silicone oils functionalized with units of HALS type. In this case, at least a portion of the symbols R5 and R6, which are alike and/or different, of the silicone oil represent a monovalent functional group chosen from a residue of formula (II) defined below such that the ratio of the number of functional groups of formula (II) to the number of Si units of the silicone oil is between 5 and 15%: 
in which:
(1) the monovalent R11 radicals are identical and/or different and are chosen from linear or branched alkyl radicals having 1 to 3 carbon atoms and the phenyl radical,
(2) the monovalent R12 radical represents a hydrogen radical,
(3) the R10 radical is a divalent hydrocarbon-comprising radical chosen from:
linear or branched alkylene radicals having 2 to 18 carbon atoms,
alkylenecarbonyl radicals, the linear or branched alkylene part of which comprises 2 to 20 carbon atoms,
alkylenecyclohexylene radicals, the linear or branched alkylene part of which comprises 2 to 12 carbon atoms and the cyclohexylene part of which comprises an OH group and optionally 1 or 2 alkyl radicals having 1 to 4 carbon atoms,
radicals of formula xe2x80x94R13xe2x80x94Oxe2x80x94R13xe2x80x94 in which the R13 radicals, which are identical or different, represent alkylene radicals having 1 to 12 carbon atoms,
radicals of formula xe2x80x94R13xe2x80x94Oxe2x80x94R13xe2x80x94 in which the R13 radicals have the meanings indicated above and one of them or both are substituted by one or two xe2x80x94OH group(s);
radicals of formula xe2x80x94R13-COOxe2x80x94R13xe2x80x94 in which the R13 radicals have the meanings indicated above,
radicals of formula xe2x80x94R14xe2x80x94Oxe2x80x94R15xe2x80x94Oxe2x80x94COxe2x80x94R14xe2x80x94 in which the R14 and R15 radicals, which are identical and/or different, represent alkylene radicals having 2 to 12 carbon atoms and the R10 radical is optionally substituted by a hydroxyl radical,
U represents xe2x80x94Oxe2x80x94 or xe2x80x94NR16xe2x80x94, R16 being a radical chosen from a hydrogen atom, a linear or branched alkyl radical comprising 1 to 6 carbon atoms and a divalent radical of formula (III): 
xe2x80x83in which R10 has the meaning indicated above, R11 and R12 have the meanings indicated above and R17 represents a linear or branched divalent alkylene radical having from 1 to 12 carbon atoms, one of the valence bonds (that of R17) being connected to the atom of xe2x80x94NR16xe2x80x94 and the other (that of R10) being connected to a silicon atom.
According to a preferred form of the invention, the ratio of the number of functional units of type (II) to the number of Si units of the silicone oil is of the order of 6%.
Furthermore, the R12 radical of the formula (II) and/or (III) can represent, in addition to a hydrogen radical, an R5 or O radical; which thus furthermore confers on the polyurethane films the improved properties of protection against UV radiation.
The silicone oil can advantageously also comprise hydroxyaryl units within its structure. These units have antioxidizing properties and properties of protection against UV radiation, the ratio of the number of these hydroxyaryl units to the number of Si units of the silicone oil being between 1 and 15%. In this case, at least a portion of the symbols R1 and R5, which are alike or different, represent a xe2x80x94(CH2)n(V) (Ar) functional group, where:
n is between 1 and 10,
the V radicals are identical and/or different and represent a divalent radical chosen from xe2x80x94NHxe2x80x94, xe2x80x94NHRxe2x80x2xe2x80x94, xe2x80x94CHNxe2x80x94, xe2x80x94Oxe2x80x94 or xe2x80x94COOxe2x80x94,
Rxe2x80x2 is a linear or branched alkyl radical having from 1 to 4 carbon atoms, and
Ar is an aromatic group substituted by at least one OH radical which can be substituted by at least one hydrocarbon-comprising radical comprising from 1 to 4 carbon atoms which can comprise a heteroatom, Ar preferably being a phenol group.
Reference will be made, as examples of hydroxyaryl units, to those disclosed in U.S. Pat. No. 4,430,235 and U.S. Pat. No. 4,879,378.
The polyisocyanate used in the context of the invention can be prepared according to various procedures and from various compounds. The characteristics of the polyisocyanate used can vary from one composition to another while remaining within the scope of the invention. For example, the polyisocyanate can be in the trimer form (ex.: isocyanate units), dimer form (ex.: uretidione units), biuret form or allophanate form or their mixture.
The polyisocyanates used in the context of the invention can be used with or without solvent. The viscosity of the polyisocyanates, as dry matter, obtained and used in the context of the invention is between 20 and 20,000 mPaxc2x7s and preferably between 100 and 11,000 mPaxc2x7s. Of course, the viscosity of the polyisocyanates given above will decrease when they are measured with solvents. In addition, the NCO content of the polyisocyanates used is between 5 and 65 weight % with respect to the dry matter of the polyisocyanate and preferably between 15 and 25 weight %.
The diisocyanates preferred in the preparation of the polyisocyanates of the compositions according to the invention are those of formula R(NCO)2, in which R is a divalent aliphatic hydrocarbon-comprising group having from 4 to 18 carbon atoms or a heterocyclo-aliphatic group in which the ring comprises from 3 to 15 carbon atoms.
As examples, the following diisocyanates are suitable for the preparation of the polyisocyanates used in the compositions of the invention:
1,4-tetramethylene diisocyanate, 1,6-hexamethylene iisocyanate, 2,2,4-trimethyl-1,6-hexamethylene iisocyanate, 1,12-dodecamethylene diisocyanate, cyclohexane 1,3-diisocyanate, cyclohexane 1,4-diisocyanate, 1-isocyanato-2-isocyanatomethylcyclopentane, 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethylcyclohexane, bis(4-isocyanatocyclohexyl)methane, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, bis(4-isocyanato-3-methylcyclohexyl)methane, xcex1,xcex1,xcex1xe2x80x2,xcex1xe2x80x2-tetramethyl-1,3- and/or -1,4-xylylene diisocyanate, 1-isocyanato-1-methyl-4(3)-isocyanatomethylcyclohexane, and 2,4- and/or 2,6-hexahydrotoluyl diisocyanate.
The polyisocyanate is preferably prepared by oligocondensation or polycondensation of polymethylene diisocyanate or its derivatives and in particular tetramethylene diisocyanate and hexamethylene diisocyanate.
It is possible, among these polycondensates or oligocondensates, to mention those prepared from mixing the diisocyanates mentioned above with monoisocyanates or polyisocyanates having at least 3 isocyanate groups. More particularly, derivatives comprising (an) isocyanuric ring(s) [denoted under the term of trimer] and derivatives exhibiting a biuret functional group should be mentioned.
Aliphatic or aromatic isocyanates, and preferably aromatic isocyanates, can dimerize at room temperature, more particularly in the presence of a dimerization catalyst, such as triethylphosphine, pyridine, triethylamine or alkoxymetallic complexes
Aliphatic or aromatic isocyanates can trimerize at high temperature, in the presence of a trimerization catalyst, such as calcium acetate, sodium formate, hexamethyldisilazane, triethylamine, triphenylphosphine or quaternary ammonium. The trimers obtained form structures which are extremely stable towards heat and towards hydrolytic attacks and are characterized by a molecular weight of between 250 and 5000.
As examples of commercial products, the products sold by Rhxc3x4ne-Poulenc and Bayer AG are appropriate for their use as polyisocyanate in the compositions of the invention. On this subject, mention will be made of the products of the Desmodur range from Bayer AG, including Desmodur N 3390 and Desmodur N 3300, or the products of the Tolonate HDT range from Rhxc3x4ne-Poulenc (Tolonate HDT LV and Tolonate HDT 90).
The hydroxylated acrylic oligomer used in the crosslinkable compositions of the invention exhibits a content by mass of hydroxyl groups of 0.1 to 10% (with respect to the dry matter) and a viscosity of 100 to 20,000 mPaxc2x7s, preferably of 1000 to 6000 mPaxc2x7s. At least a portion of the OH groups present in the acrylic oligomer are reactive with respect to isocyanate groups during the formation of the polyurethane films from the crosslinkable compositions of the invention.
As examples, the acrylic oligomers comprising hydroxyl groups which can be used in the context of the invention are chosen from: 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate and 3-hydroxypropyl methacrylate.
The acrylic oligomers are generally used in the solution form in solvents and have a viscosity of 4000 to 10,000 mPaxc2x7s. Various types of solvents can be used, for example hydrocarbons, esters and ketones, and the like. The solvent used is preferably based on methyl amyl ketone and/or on butyl acetate and additionally comprises other solvents with different boiling points. The solvent used is preferably methyl amyl ketone. The concentration by weight of acrylic oligomer in the solution of the said oligomer is generally between 40 and 80%. In the case where methyl amyl ketone is used as solvent, the concentration by weight of acrylic oligomer is between 50 and 80%. However, it is possible to use acrylic oligomers without solvent in the context of the invention.
As examples of commercial products, the products sold by the companies Rhxc3x4ne-Poulenc, Dupont de Nemours, Johnson, Akzo, Hoechst, Cray Valley and Croda are suitable for their use as hydroxylated acrylic oligomer in the compositions of the invention. Mention will more particularly be made of the products of the Johnson SCX range, in particular 910 and 920, the products of the Setalux range (1753 SS 60, and the like), the products of the Macrynal range (SM 510, and the like), the products of the Synocure range and the products of the Crodaplast range.
Polyurethane films can be prepared from the crosslinkable compositions according to various techniques, in particular by chemical curing, thermal curing, UV radiation or the use of an electron beam.
According to a preferred alternative preparative form, the polyurethane films are obtained by heat treatment at a temperature of between 50 and 200xc2x0 C. and advantageously between 80 and 150xc2x0 C. Furthermore, the best results are obtained in the presence of a catalyst, such as dibutyltin dilaurate, tin octanoate or dibutyltin diacetate, thus promoting the reactions between the silicone oil, the polyol and the polyisocyanate. The catalyst used is advantageously dibutytin dilaurate. Other catalysts can also be used to prepare the polyurethane films; on this subject, reference will in particular be made to the document EP 524,501 A1. The catalyst is preferably added immediately before the addition of the polyisocyanate.
As example, the process for the preparation by heat treatment of a polyurethane film comprises the stages consisting in:
(1) mixing the solvent, the hydroxylated oligomer and the silicone oil,
(2) adding the polyisocyanate to and mixing with the mixture obtained in (1),
(4) spreading the mixture over a surface to be coated, and
(5) drying the spread mixture and then curing it at a temperature of between 50xc2x0 C. and 200xc2x0 C. for 20 minutes to 1 hour.
As alternative form for the preparation of polyurethane films from crosslinkable compositions according to the invention, the silicone oil is mixed with the acrylic oligomer. The polyisocyanate, the solvent and, optionally, the catalyst are then added to this mixture. It is also possible to bring a portion of the polyisocyanate into contact with the silicone oil beforehand. After these two compounds have reacted with one another, they are then mixed with the acrylic oligomer, the polyisocyanate, if necessary, the solvent and, optionally, the catalyst.
In agreement with the invention, the operating conditions for the preparation of polyurethane films and the compounds of the crosslinkable compositions, i.e. qualities and amounts, are chosen in order for the NCO/XH molar ratio of the polyurethane films to be between 0.5 and 1.5 and preferably between 0.95 and 1.1; NCO being the isocyanate functional group of the polyisocyanate and XH representing OH, NH and SH, which are the reactive functional groups of the acrylic polymer and those of the functionalized silicone oil.
In particular, the controlled miscibility of the silicone oil within the acrylic oligomer and polyisocyanate system allows this oil to migrate at a relatively low rate towards the surface of the said film when it is formed, this low rate furthermore allowing the groups of the silicone oil carrying active hydrogens to react with the polyisocyanate. Thus, most of the silicone oil is found in the surface layer of the film and is fixed in the polyurethane matrix by chemical bonding, which contributes permanent anti-scratching properties, even after the film has been washed several times, confirmed by the examples.
The improvement in the anti-scratching properties is observed in particular by a better gloss of the surface of the film which prevents scratch formation. If, however, scratching occurs, the silicone oil present in the surface layer of the film fills in the scratch (achievement of a minimum energy state), which allows the scratch to be stopped up (healing effect).
The field of use of the polyurethane films obtained from the crosslinkable compositions of the invention is highly varied. The films obtained from the crosslinkable compositions according to the invention can be used equally well for a mass-production coating, a protective coating or for a repair coating. The coatings can, for example, be paints and varnishes. In addition, the films can comprise any conventional pigment (for example for colouring) and additive, such as agents for protecting against light, antioxidizing agents, levelling agents, and the like. As regards the agents for protecting against light, it has been specified previously that the silicone oils used can advantageously be functionalized with functional groups of formula (II) which are radical scavengers of HALS type, i.e. agents which stabilize with respect to light comprising sterically hindered amines, and/or hydroxyaryl functional groups. In this case, the films can comprise, on the one hand, silicone oils functionalized with HALS functional groups and/or hydroxyaryl functional groups and, on the other hand, if necessary, agents for protecting against light, including those with functional groups of HALS type.